The present invention relates to the combining of radio signals in accordance with a technique known as diversity combining. More particularly, the present invention relates to the reconfiguration of diversity legs and the establishment of transport level connections, which support the diversity legs, during a change in the location of the diversity combining unit within the telecommunication network.
A typical mobile communications network, such as the mobile network 100 illustrated in FIG. 1, includes a number of elements. For instance, the mobile network 100 includes a core network CN, a radio access network RAN and multiple user equipment terminals (e.g., cellular telephones), such as mobile equipment terminal UE. The RAN, in turn, comprises a number of common elements or nodes. For example, the RAN illustrated in FIG. 1 comprises several base stations, BS1, BS2, BS3 and BS4, as well as several radio network controllers, SRNC, DRNC1 and DRNC2. Through the RAN, the user equipment terminal UE accesses services provided by the core network CN.
Generally, each base station BS1, BS2, BS3 and BS4 controls the radio connectivity in a corresponding geographic area known as a cell. Each RNC, in turn, controls the radio connectivity inside a given geographic area which covers one or more base stations. In FIG. 1, for example, the SRNC handles the geographic area that includes BS1, the DRNC1 handles the geographic area that includes BS2 and BS4, and DRNC2 handles the geographic area that includes BS3.
The RNCs serve in one of two capacities. First, an RNC can be a serving RNC (i.e., an SRNC). Second, a RNC can be a drift RNC (i.e., a DRNC). A SRNC provides the primary source of control over the connection between user equipment UE and the core network CN, wherein the SRNC communicates directly with the core network CN through the CN-RNC interface. In contrast, a DRNC, such as DRNC1 or DRNC2, supports the SRNC with radio resources for its connection with the user equipment UE. DRNCs communicate with the SRNC over an RNC-RNC interface. RNCs communicate with their corresponding base stations over an RNC-BS interface.
As will be explained in more detail below, the role of an RNC can change during the course of a UE connection (e.g., a telephone call). For example, as the UE travels from one cell to the next, a DRNC may be converted to a SRNC through a CN-RNC interface streamlining process, also known in the art as Iu streamlining. During CN-RNC interface streamlining, the CN-RNC interface which connects a SRNC to the core network is transferred from an original SRNC to a new SRNC.
In a mobile communications network, such as the mobile network 100 depicted in FIG. 1, radio signals are often impaired due to a variety of phenomena such as time dispersion, multipath fading and co-channel and/or adjacent channel interference. In order to mitigate signal impairment, a technique known as diversity combining/splitting herein referred to as diversity combining) is often employed. With diversity combining, a number of simultaneous radio and/or network connections, called diversity legs are established between the user equipment UE and two or more sectors of a single base station, two or more base stations and/or two or more RNCs. FIG. 2 illustrates a UE connection that presently has five radio diversity legs 1-5 and three network diversity legs A,B,C.
In accordance with diversity combining, diversity legs are combined at the various network nodes (i.e., the base stations and RNCs) until they are ultimately combined into a single data stream by the SRNC. By combining diversity legs, as described, any impairment affecting the radio signal associated with one diversity leg is typically compensated for by the radio signal associated with one or more of the other diversity legs.
In the RAN portion of the mobile communications network 100, which includes the connections between the base stations and the RNCs and between the RNCs, each network diversity leg is supported by a corresponding transport level connection at the RNC-RNC and/or RNC-BS interface. As one skilled in the art will readily appreciated, each network diversity leg represents a logical connection between two end points, for example, BS1 and the SRNC, whereas a corresponding transport level connection is a functional layer within a layered network architecture design that is responsible for conveying the signals associated with the network diversity leg.
As the user equipment UE moves about within the mobile communications network 100, the primary responsibility for controlling the connection between the user equipment UE and the core network CN may change. In fact, it may become necessary to relocate the diversity combining unit, herein referred to as the diversity handoff unit (DHO), from the present SRNC to a new SRNC. For example, in FIG. 1, if the user equipment UE travels from the cell associated with BS1 into the cell associated with BS2, such that a mobile assisted hand-off (MAHO) occurs between BS1 and BS2, the DHO for the connection may be relocated from the SRNC to the DRNC1. If the DHO unit is relocated, what was the SRNC will now be a DRNC, as shown in FIG. 3, and what was the DRNC1 will now be the SRNC. The process of relocating the DHO from the original SRNC to a new SRNC is called CN-RNC interface streamlining, as mentioned above. In order to properly relocate the DHO, an effective technique is required to reconfigure the various network diversity legs and to establish the transport level connections which are needed to support them.
The present invention involves a technique for effectively accomplishing CN-RNC interface streamlining in a mobile communications network, such as a cellular radio access network. The present invention accomplishes this, in part, by providing an efficient method for reconfiguring the various network diversity legs and for establishing the transport level connections which support them. Accordingly, it is an object of the present invention to provide a technique for relocating the diversity handover unit (DHO) from one radio network controller to another.
It is another object of the present invention to provide an efficient technique for reconfiguring the various network diversity legs, if necessary, during the relocation of a DHO in a radio telecommunications network that employs diversity combining.
It is still another object of the present invention to provide an efficient technique for releasing and reestablishing the transport level connections needed to support the reconfigured network diversity legs, during the relocation of a DHO.
In accordance with one aspect of the present invention, the above-identified and other objects are achieved by a method for reconfiguring network diversity legs during CN-RNC interface streamlining. The method involves transferring destination address and binding information from a first radio network controller to a second radio network controller. A number of transport level connections are then released, wherein each of the transport level connections were utilized to support a corresponding network diversity leg, and a new transport level connection between the second radio network controller and each of a plurality of destination nodes is established by dispatching a destination address and binding information from the second radio network controller to each of the destination nodes. One or more resources at each destination node are then bound to support a corresponding network diversity leg between each destination node and the second radio network controller, based on the binding information dispatched to each destination node.
In accordance with another aspect of the present invention, the above-identified and other objects are achieved by a method for reconfiguring network diversity legs during CN-RNC interface streamlining, wherein each network diversity leg is supported by a corresponding asynchronous transfer method (ATM) adaptation layer type 2 (AAL2) transport level connection. The method involves transferring destination address and binding information from an old serving radio network controller to a new serving radio network controller, and releasing a number of AAL2 transport level connections, wherein each of the released AAL2 transport level connections were used to support a network diversity leg between a destination node and a diversity handover unit in the old serving radio network controller. An AAL2 set-up message is then transported from the new serving radio network controller to each of a number of destination nodes, in accordance with an existing address associated with each of the destination nodes, wherein each AAL2 set-up message contains binding information pertaining to a corresponding destination node. At each destination node, the corresponding AAL2 connection is bound to one or more resources, based on the binding information corresponding to the destination node, wherein the one or more resources are used to support a corresponding network diversity leg between the destination node and the diversity handover unit in the new serving radio network controller.